The shovel is a well known hand tool used primarily for transfer of loose objects from one location to another. Despite the use, a primary concern with shovel design is the strength to weight ratio. Typically the stronger a shovel, the heavier it is, due to the amount of material mass required for rigidity. For instance, the blade of a shovel made from steel is suitable for transferring of heavy material. However, the weight of steel becomes critical if the blade is to be lifted, especially if the person lifting the blade is not trained in proper lifting techniques. If the blade is made too thin, it will bend under load. Thus, a shovel constructed from steel is typically of a thickness to make the weight noticeable creating a hand tool that is hefty to operate.
Further, since a shovel blade is used to move material, it is constantly subjected to abrasion which will quickly deteriorate even high quality finishes. This leads to premature failure of the tool especially in areas of the country where the tool is used for snow removal. The combination of moisture and possible road salt can quickly rust steel tools.
A shovel used primarily for snow removal is unique in that the consumer seeks as large a blade as possible yet demands minimal weight. For this reason, in place of a steel blade manufacturers now provide alternative materials such as aluminum and plastic. It is noted that while aluminum does not rust it is much weaker than steel and requires either sufficient thickness or steel reinforcement in order to withstand the strain. Without reinforcement of an aluminum blade to prevent counter-flexing, such as stepping on the back of the blade, the aluminum blade can easily bend in half thereby ruining the tool.
Another problem with the shovels of the prior art is that the shaft and associated handle further add to the weight of the tool leaving manufacturers to try to remedy the situation with various types of materials. In this instance steel is most suitable when used as tubing but is not used due to weight for the shaft and handle due to the inability to compensate for the retainment of the surrounding ambient temperature when used during frigid months. Further, since a steel shaft and handle must be painted, the operator can easily wear off the coating since both must be grasped in an abrasive manner quickly leading to rust abrasion.
Common practice is to make the shaft from wood and to rivet a section of wood to the handle. However, a problem with wood is that unless properly treated, water can rot the wood especially where the components are coupled together. While it is possible to replace the wood, it is more likely that the tool will be disposed of.
The blade, shaft and handle of a shovel can also be constructed from plastic which does not rot, rust, or retain cold as its wood and steel counterparts. However, the problem with plastic is strength. A plastic shaft may flex causing the shaft to bend since the shaft becomes a fulcrum point during use. A blade made of plastic further presents a number of problems including control of flexing and wear.
U.S. Pat. No. 4,280,727 discloses a one piece plastic injected molded snow shovel in which the blade, shaft and handle are molded in a single operation. The disclosure illustrates the conventional wisdom of plastic when used for a snow shovel. In particular, blade flex is controlled by use of parallel spaced apart ribs in a similar manner as used with aluminum construction. However, plastic does not flex like metal; thus, the thickness of the plastic must be increased to provide sufficient strength. The shaft of the shovel also demonstrates the complications when a shaft is formed entirely from plastic by claiming a complicated cross pattern that is expensive to manufacture.
Thus, what is needed in the art is a light weight shovel having an improved plastic blade that compensates for flexing providing superior rigidity and a shaft having the rigidity of steel yet the superior properties of plastic.